Russia and Brazil, on the other hand, are flailing, and could soon lose membership in that club of emerging-market powerhouses, O'Neill said.

Brazil's economy is only expected to grow 1% this year, and Russia's will actually contract 1.8 percent, according to the report.

Meanwhile, China's growth, measured by purchasing-power parity, will add twice as much to global output as the United States', and India's growth will double that of the United Kingdom by those terms, O'Neill said. No wonder they would want to ditch the others.